Intramural Valves of Lymphatic Capillaries of Intestinal Villi in Rats

Abstract

The article highlights a complex of interendothelial connections of the lymphatic capillary of the rat intestinal villi, and focuses on the path of chylomicron transport through the lymphatic capillary wall after lipid loading.Material and methods. An experimental model was used to exclude a high lipid load; chymus from do- nor rats was injected with a syringe into the initial section of the small intestine in 10 Wistar rats. Chymus was collected from the initial section of the small intestine of donor animals 60 min after oral administration of 1.5 ml of corn oil. The control group consisted of the animals exposed to 12-hour fasting. The material was studied using transmission electron microscopy.Results. It was shown that most often cells are connected by tile-like (66±2.2%) or simple finger-like (27±2.4%) contacts, reinforced with a tight connection and a point adhesive (at the extreme point of contact). An- chor filaments located on the basal surface of endothelial cells at some distance from the extreme contact point “fixed” the lymphatic capillary wall, ensuring its stretching, changing the pressure inside the capillary and opening the valve. Under low lipid load, the main transport pathway of lipids from the interstitium of the intestinal villus to the lumen of the lymphatic capillary was through adhesive intercellular contacts. No chylomicrons were found in the lumen of plasmolemmal vesicles and kidneys. Caveolae in the endothelial cells of the lymphatic capillary, both after lipid loading and in hungry animals, were few. Caveolosomes were rare in both groups. Under low lipid load, no fusion of vesicles with the formation of transendothelial canals was found.Conclusions. The detected structure of contacts of the lymphatic capillary endothelium morphologically substantiates the hypothesis of the regulated resorption of interstitial fluid and macromolecules into the lumen of the lymphatic capillary.